feat(web): Kalender-Widget neu gebaut mit Monatsraster + Naechste Termine, Mindestgroesse 6x8

- calendar-widget.tsx komplett neu: Monatsraster (Nav-Zeile, Wochentagskopf, 42 Zellen, heutiger Tag, Zaehl-Plakette, Portal-Tooltip) + Block "Naechste Termine"; fetchEvents bekommt immer zwei Tagesgrenzen-ISO-Strings ueber computeFetchWindow
- Komponententest komplett neu geschrieben (9 Tests: Laden/Quellen, Raster, Plakette, Tooltip inkl. 5+-Kuerzung, Naechste-Termine-Filter, showMonth/maxEvents=0, Ladefenster, Blaettern)
- WIDGET_CONSTRAINTS.calendar auf { minW: 6, minH: 8, defaultW: 8, defaultH: 12 } angehoben (quick-260916-htc), Registry-Test A mitgezogen

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

apps/web/src/components/dashboard/widget-registry.test.tsx

@@ -61,7 +61,7 @@ describe('WIDGET_CONSTRAINTS (DASH-11)', () => {
     expect(WIDGET_CONSTRAINTS).toEqual({
       clock: { minW: 2, minH: 2, defaultW: 4, defaultH: 4 },
       search: { minW: 6, minH: 2, defaultW: 12, defaultH: 4 },
-      calendar: { minW: 3, minH: 3, defaultW: 8, defaultH: 12 },
+      calendar: { minW: 6, minH: 8, defaultW: 8, defaultH: 12 },
       note: { minW: 4, minH: 4, defaultW: 6, defaultH: 8 },
       calculator: { minW: 3, minH: 10, defaultW: 6, defaultH: 10 },
       favorites: { minW: 3, minH: 3, defaultW: 6, defaultH: 10 },

apps/web/src/components/dashboard/widget-registry.tsx

@@ -41,7 +41,9 @@ export const WIDGET_CONSTRAINTS: Record<
   // Existing widgets
   clock: { minW: 2, minH: 2, defaultW: 4, defaultH: 4 },
   search: { minW: 6, minH: 2, defaultW: 12, defaultH: 4 },
-  calendar: { minW: 3, minH: 3, defaultW: 8, defaultH: 12 },
+  // quick-260916-htc: Monatsraster braucht Breite fuer 7 Spalten und Hoehe
+  // fuer Nav-Zeile + Wochentagskopf + 6 Rasterzeilen + Naechste-Termine-Block.
+  calendar: { minW: 6, minH: 8, defaultW: 8, defaultH: 12 },
   note: { minW: 4, minH: 4, defaultW: 6, defaultH: 8 },
   // Phase 8 new widgets (D-01)
   // minH 10, nicht 9 (260916-dyv, Browser-Messung des Orchestrators): der Rechner hat

apps/web/src/components/dashboard/widgets/calendar-widget.test.tsx

@@ -1,19 +1,35 @@
-import { cleanup, render, screen, waitFor } from '@testing-library/react';
+import { cleanup, fireEvent, render, screen, waitFor, within } from '@testing-library/react';
 import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest';
+import type { CalendarEvent } from '@/lib/calendar-api';
 
-// Mock next-intl
+/**
+ * calendar-widget.test — neu geschrieben (quick-260916-htc). Ersetzt die
+ * alten drei Tests der flachen Terminliste durch Tests fuer das
+ * Monatsraster, den Portal-Tooltip, "Naechste Termine" und das
+ * Ladefenster/Blaettern.
+ */
+
+// Mock next-intl — nimmt (key, values?) und ersetzt {name}-Platzhalter.
 vi.mock('next-intl', () => ({
-  useTranslations: (ns: string) => (key: string) => {
+  useTranslations: (ns: string) => (key: string, values?: Record<string, unknown>) => {
     const map: Record<string, Record<string, string>> = {
       widgets: {
-        'calendar.name': 'Calendar',
-        'calendar.description': 'Upcoming events',
-        'calendar.emptyNoSources': 'No calendar sources configured',
-        'calendar.emptyNoEvents': 'No upcoming events',
-        'calendar.loading': 'Loading...',
+        'calendar.name': 'Kalender',
+        'calendar.description': 'Kommende Termine',
+        'calendar.loading': 'Laden...',
+        'calendar.emptyNoSources': 'Keine Kalenderquellen konfiguriert',
+        'calendar.emptyNoEvents': 'Keine anstehenden Termine',
+        'calendar.nothingSelected': 'Nichts zum Anzeigen ausgewählt',
+        'calendar.monthPrev': 'Zurück',
+        'calendar.monthNext': 'Weiter',
+        'calendar.monthToday': 'Zurück zum heutigen Monat',
+        'calendar.upcomingTitle': 'Nächste Termine',
+        'calendar.tooltipMore': 'Weitere Termine vorhanden',
+        'calendar.allDay': 'ganztägig',
       },
     };
-    return map[ns]?.[key] ?? key;
+    const raw = map[ns]?.[key] ?? key;
+    return values ? raw.replace(/\{(\w+)\}/g, (_, n) => String(values[n] ?? '')) : raw;
   },
 }));
 
@@ -25,96 +41,259 @@ vi.mock('@/lib/calendar-api', () => ({
   fetchSources: (...args: unknown[]) => mockFetchSources(...args),
 }));
 
+function ev(id: string, start: Date, end: Date, extra?: Partial<CalendarEvent>): CalendarEvent {
+  return {
+    id,
+    sourceId: 's1',
+    title: id,
+    start: start.toISOString(),
+    end: end.toISOString(),
+    allDay: false,
+    ...extra,
+  };
+}
+
+beforeEach(() => {
+  mockFetchEvents.mockReset();
+  mockFetchSources.mockReset();
+  vi.useFakeTimers({ toFake: ['Date'] });
+  vi.setSystemTime(new Date(2026, 6, 15, 10, 0, 0));
+  mockFetchSources.mockResolvedValue([
+    { id: 's1', name: 'Work', type: 'caldav', isVisible: true, color: '#ff0000' },
+  ]);
+});
+
 afterEach(() => {
+  vi.useRealTimers();
   cleanup();
   vi.restoreAllMocks();
 });
 
 describe('CalendarWidget', () => {
-  beforeEach(() => {
-    // Default: sources exist so we get past the source check
-    mockFetchSources.mockResolvedValue([
-      { id: 's1', name: 'Work', type: 'caldav', isVisible: true, color: '#ff0000' },
-    ]);
-  });
-
-  it('renders event titles, times, and source color dots for two events', async () => {
-    mockFetchEvents.mockResolvedValue([
-      {
-        id: 'e1',
-        sourceId: 's1',
-        title: 'Team Meeting',
-        start: '2026-06-24T10:00:00Z',
-        end: '2026-06-24T11:00:00Z',
-        allDay: false,
-        color: '#ff0000',
-      },
-      {
-        id: 'e2',
-        sourceId: 's1',
-        title: 'Lunch Break',
-        start: '2026-06-24T12:00:00Z',
-        end: '2026-06-24T13:00:00Z',
-        allDay: false,
-        color: '#00ff00',
-      },
-    ]);
-
-    const { CalendarWidget } = await import('./calendar-widget');
-    render(
-      <CalendarWidget
-        instanceId="cal-1"
-        config={{}}
-        isEditMode={false}
-      />,
-    );
-
-    // Wait for events to load
-    await waitFor(() => {
-      expect(screen.getByText('Team Meeting')).toBeInTheDocument();
-    });
-
-    expect(screen.getByText('Lunch Break')).toBeInTheDocument();
-
-    // Source color dots should be rendered (8px circles)
-    const colorDots = screen.getAllByTestId('event-color-dot');
-    expect(colorDots).toHaveLength(2);
-  });
-
-  it('renders no-events message when sources exist but no events returned', async () => {
-    mockFetchEvents.mockResolvedValue([]);
-
-    const { CalendarWidget } = await import('./calendar-widget');
-    render(
-      <CalendarWidget
-        instanceId="cal-2"
-        config={{}}
-        isEditMode={false}
-      />,
-    );
-
-    await waitFor(() => {
-      expect(screen.getByText('No upcoming events')).toBeInTheDocument();
-    });
-  });
-
-  it('renders no-sources message when no sources configured', async () => {
+  it('Test 1: zeigt Laden, dann bei leeren Quellen die Keine-Quellen-Meldung ohne fetchEvents', async () => {
     mockFetchSources.mockResolvedValue([]);
+
+    const { CalendarWidget } = await import('./calendar-widget');
+    render(<CalendarWidget instanceId="cal-1" config={{}} isEditMode={false} />);
+
+    expect(screen.getByText('Laden...')).toBeInTheDocument();
+
+    await waitFor(() => {
+      expect(screen.getByText('Keine Kalenderquellen konfiguriert')).toBeInTheDocument();
+    });
+    expect(mockFetchEvents).not.toHaveBeenCalled();
+  });
+
+  it('Test 2: rendert das Monatsraster mit 42 Zellen, heutigem Tag und Fremdmonatstagen', async () => {
     mockFetchEvents.mockResolvedValue([]);
 
     const { CalendarWidget } = await import('./calendar-widget');
-    render(
-      <CalendarWidget
-        instanceId="cal-3"
-        config={{}}
-        isEditMode={false}
-      />,
+    render(<CalendarWidget instanceId="cal-2" config={{}} isEditMode={false} />);
+
+    await waitFor(() => {
+      expect(screen.getByText('Juli 2026')).toBeInTheDocument();
+    });
+
+    for (const label of ['Mo', 'Di', 'Mi', 'Do', 'Fr', 'Sa', 'So']) {
+      expect(screen.getAllByText(label).length).toBeGreaterThan(0);
+    }
+
+    const dayCells = screen.getAllByTestId('calendar-day');
+    expect(dayCells).toHaveLength(42);
+
+    const todayCell = document.querySelector('[data-date="2026-07-15"]');
+    expect(todayCell?.getAttribute('data-today')).toBe('true');
+    expect(todayCell?.textContent).toContain('15');
+    expect(within(todayCell as HTMLElement).queryByTestId('calendar-day-count')).toBeNull();
+
+    const outsideCell = document.querySelector('[data-date="2026-06-29"]');
+    expect(outsideCell?.getAttribute('data-outside')).toBe('true');
+
+    const monthBlock = screen.getByTestId('calendar-month');
+    expect(monthBlock.className).toContain('');
+    for (const btn of screen.getAllByRole('button')) {
+      expect(btn.className).toContain('widgetNoDrag');
+    }
+    for (const cell of dayCells) {
+      expect(cell.className).toContain('widgetNoDrag');
+    }
+
+    expect(screen.getByText('Nächste Termine')).toBeInTheDocument();
+    expect(screen.getByText('Keine anstehenden Termine')).toBeInTheDocument();
+  });
+
+  it('Test 3: Zaehl-Plakette zeigt die korrekte Terminanzahl je Tag', async () => {
+    mockFetchEvents.mockResolvedValue([
+      ev('Team Meeting', new Date(2026, 6, 20, 9, 0), new Date(2026, 6, 20, 10, 0)),
+      ev('Lunch', new Date(2026, 6, 20, 14, 0), new Date(2026, 6, 20, 15, 0)),
+      ev('Review', new Date(2026, 6, 21, 10, 0), new Date(2026, 6, 21, 11, 0)),
+    ]);
+
+    const { CalendarWidget } = await import('./calendar-widget');
+    render(<CalendarWidget instanceId="cal-3" config={{}} isEditMode={false} />);
+
+    await waitFor(() => {
+      expect(screen.getByText('Juli 2026')).toBeInTheDocument();
+    });
+
+    const day20 = document.querySelector('[data-date="2026-07-20"]') as HTMLElement;
+    expect(within(day20).getByTestId('calendar-day-count')).toHaveTextContent('2');
+
+    const day21 = document.querySelector('[data-date="2026-07-21"]') as HTMLElement;
+    expect(within(day21).getByTestId('calendar-day-count')).toHaveTextContent('1');
+
+    const day22 = document.querySelector('[data-date="2026-07-22"]') as HTMLElement;
+    expect(within(day22).queryByTestId('calendar-day-count')).toBeNull();
+  });
+
+  it('Test 4: Tooltip erscheint per Portal im body und zeigt bis zu 5 Termine plus Hinweis', async () => {
+    mockFetchEvents.mockResolvedValue([
+      ev('Team Meeting', new Date(2026, 6, 20, 9, 0), new Date(2026, 6, 20, 10, 0)),
+      ev('Lunch', new Date(2026, 6, 20, 14, 0), new Date(2026, 6, 20, 15, 0)),
+    ]);
+
+    const { CalendarWidget } = await import('./calendar-widget');
+    render(<CalendarWidget instanceId="cal-4" config={{}} isEditMode={false} />);
+
+    await waitFor(() => {
+      expect(screen.getByText('Juli 2026')).toBeInTheDocument();
+    });
+
+    const day20 = document.querySelector('[data-date="2026-07-20"]') as HTMLElement;
+    fireEvent.mouseEnter(day20);
+
+    const tooltip = screen.getByTestId('calendar-day-tooltip');
+    expect(document.body.contains(tooltip)).toBe(true);
+    expect(tooltip).toHaveTextContent('09:00');
+    expect(tooltip).toHaveTextContent('Team Meeting');
+    expect(tooltip).toHaveTextContent('Lunch');
+
+    fireEvent.mouseLeave(day20);
+    expect(screen.queryByTestId('calendar-day-tooltip')).toBeNull();
+  });
+
+  it('Test 4b: Tooltip zeigt maximal 5 Eintraege plus Hinweis bei mehr Terminen', async () => {
+    mockFetchEvents.mockResolvedValue([
+      ev('e1', new Date(2026, 6, 20, 8, 0), new Date(2026, 6, 20, 9, 0)),
+      ev('e2', new Date(2026, 6, 20, 9, 0), new Date(2026, 6, 20, 10, 0)),
+      ev('e3', new Date(2026, 6, 20, 10, 0), new Date(2026, 6, 20, 11, 0)),
+      ev('e4', new Date(2026, 6, 20, 11, 0), new Date(2026, 6, 20, 12, 0)),
+      ev('e5', new Date(2026, 6, 20, 12, 0), new Date(2026, 6, 20, 13, 0)),
+      ev('e6', new Date(2026, 6, 20, 13, 0), new Date(2026, 6, 20, 14, 0)),
+    ]);
+
+    const { CalendarWidget } = await import('./calendar-widget');
+    render(<CalendarWidget instanceId="cal-4b" config={{}} isEditMode={false} />);
+
+    await waitFor(() => {
+      expect(screen.getByText('Juli 2026')).toBeInTheDocument();
+    });
+
+    const day20 = document.querySelector('[data-date="2026-07-20"]') as HTMLElement;
+    fireEvent.mouseEnter(day20);
+
+    const tooltip = screen.getByTestId('calendar-day-tooltip');
+    expect(tooltip).toHaveTextContent('Weitere Termine vorhanden');
+    for (const id of ['e1', 'e2', 'e3', 'e4', 'e5']) {
+      expect(tooltip).toHaveTextContent(id);
+    }
+    expect(tooltip).not.toHaveTextContent('e6');
+  });
+
+  it('Test 5: Naechste Termine respektiert maxEvents, Reihenfolge und zeigt Ort/Farbpunkt', async () => {
+    mockFetchEvents.mockResolvedValue([
+      ev('E1', new Date(2026, 6, 16, 9, 0), new Date(2026, 6, 16, 10, 0)),
+      ev('E2', new Date(2026, 6, 18, 9, 0), new Date(2026, 6, 18, 10, 0), { location: 'Raum 2' }),
+      ev('E3', new Date(2026, 6, 22, 9, 0), new Date(2026, 6, 22, 10, 0)),
+      ev('E4', new Date(2026, 6, 26, 9, 0), new Date(2026, 6, 26, 10, 0)),
+      ev('E5', new Date(2026, 6, 30, 9, 0), new Date(2026, 6, 30, 10, 0)),
+    ]);
+
+    const { CalendarWidget } = await import('./calendar-widget');
+    render(<CalendarWidget instanceId="cal-5" config={{ maxEvents: 2 }} isEditMode={false} />);
+
+    await waitFor(() => {
+      expect(screen.getByTestId('calendar-upcoming')).toBeInTheDocument();
+    });
+
+    const list = within(screen.getByTestId('calendar-upcoming'));
+    const items = list.getAllByRole('listitem');
+    expect(items).toHaveLength(2);
+    expect(items[0]).toHaveTextContent('E1');
+    expect(items[1]).toHaveTextContent('E2');
+    expect(items[1]).toHaveTextContent('Raum 2');
+
+    for (const item of items) {
+      expect(within(item).getByTestId('event-color-dot')).toBeInTheDocument();
+    }
+    expect(items[0].textContent).toMatch(/\d{2}\.\d{2}\./);
+  });
+
+  it('Test 6: showMonth=false blendet das Raster aus, maxEvents=0 zeigt die Leermeldung', async () => {
+    mockFetchEvents.mockResolvedValue([]);
+
+    const { CalendarWidget } = await import('./calendar-widget');
+    const { unmount } = render(
+      <CalendarWidget instanceId="cal-6a" config={{ showMonth: false, maxEvents: 3 }} isEditMode={false} />,
     );
 
     await waitFor(() => {
-      expect(
-        screen.getByText('No calendar sources configured'),
-      ).toBeInTheDocument();
+      expect(screen.getByText('Keine anstehenden Termine')).toBeInTheDocument();
     });
+    expect(screen.queryByTestId('calendar-month')).toBeNull();
+    unmount();
+
+    render(<CalendarWidget instanceId="cal-6b" config={{ showMonth: false, maxEvents: 0 }} isEditMode={false} />);
+    await waitFor(() => {
+      expect(screen.getByText('Nichts zum Anzeigen ausgewählt')).toBeInTheDocument();
+    });
+    expect(screen.queryByTestId('calendar-month')).toBeNull();
+    expect(screen.queryByTestId('calendar-upcoming')).toBeNull();
+  });
+
+  it('Test 7: fetchEvents wird genau einmal mit dem berechneten Ladefenster aufgerufen', async () => {
+    mockFetchEvents.mockResolvedValue([]);
+
+    const { CalendarWidget } = await import('./calendar-widget');
+    const { unmount } = render(<CalendarWidget instanceId="cal-7a" config={{}} isEditMode={false} />);
+
+    await waitFor(() => expect(mockFetchEvents).toHaveBeenCalledTimes(1));
+    expect(mockFetchEvents).toHaveBeenCalledWith(
+      new Date(2026, 5, 29).toISOString(),
+      new Date(2026, 7, 14).toISOString(),
+    );
+    unmount();
+
+    mockFetchEvents.mockClear();
+    render(<CalendarWidget instanceId="cal-7b" config={{ lookaheadDays: 90 }} isEditMode={false} />);
+    await waitFor(() => expect(mockFetchEvents).toHaveBeenCalledTimes(1));
+    expect(mockFetchEvents.mock.calls[0][1]).toBe(new Date(2026, 9, 13).toISOString());
+  });
+
+  it('Test 8: Blaettern wechselt den Monat und laedt Termine mit dem neuen Fenster neu', async () => {
+    mockFetchEvents.mockResolvedValue([]);
+
+    const { CalendarWidget } = await import('./calendar-widget');
+    render(<CalendarWidget instanceId="cal-8" config={{}} isEditMode={false} />);
+
+    await waitFor(() => expect(screen.getByText('Juli 2026')).toBeInTheDocument());
+    mockFetchEvents.mockClear();
+
+    fireEvent.click(screen.getByRole('button', { name: 'Weiter' }));
+    await waitFor(() => expect(screen.getByText('August 2026')).toBeInTheDocument());
+    // computeFetchWindow nimmt das FRUEHERE von Rasterstart (27.07.) und
+    // heutigem Tag (15.07., "now" bleibt im Test eingefroren) als "from" —
+    // dieselbe Regel wie in calendar-month.test.ts Test 4 (w2-Fall), deshalb
+    // 15.07. statt 27.07. (Abweichung vom im Plan genannten Wert, siehe SUMMARY).
+    await waitFor(() => expect(mockFetchEvents).toHaveBeenCalledWith(
+      new Date(2026, 6, 15).toISOString(),
+      new Date(2026, 8, 7).toISOString(),
+    ));
+
+    fireEvent.click(screen.getByRole('button', { name: 'August 2026' }));
+    await waitFor(() => expect(screen.getByText('Juli 2026')).toBeInTheDocument());
+
+    fireEvent.click(screen.getByRole('button', { name: 'Zurück' }));
+    await waitFor(() => expect(screen.getByText('Juni 2026')).toBeInTheDocument());
   });
 });

apps/web/src/components/dashboard/widgets/calendar-widget.tsx

@@ -1,19 +1,46 @@
 'use client';
 
-import { useEffect, useRef, useState } from 'react';
+import { useCallback, useEffect, useMemo, useRef, useState } from 'react';
+import { createPortal } from 'react-dom';
 import { useTranslations } from 'next-intl';
 import type { WidgetProps } from '../widget-registry';
 import { fetchEvents, fetchSources } from '@/lib/calendar-api';
 import type { CalendarEvent } from '@/lib/calendar-api';
+import {
+  buildCalendarDays,
+  computeFetchWindow,
+  formatEventDate,
+  formatEventTime,
+  formatMonthLabel,
+  groupEventsByDate,
+  resolveCalendarConfig,
+  selectUpcomingEvents,
+  WEEKDAY_LABELS,
+} from './calendar-month';
 
 /**
- * Calendar widget (DASH-05, D-10 read-only).
+ * Calendar widget (DASH-05, D-10 read-only), neu gebaut nach dem Vorbild des
+ * alten persoenlichen Dashboards des Anwenders (quick-260916-htc).
  *
- * Shows upcoming events aggregated from visible calendar sources.
- * Three states per UI-SPEC:
- * 1. No sources configured -> t('widgets.calendar.emptyNoSources')
- * 2. Sources but no events -> t('widgets.calendar.emptyNoEvents')
- * 3. Events -> upcoming-events list with time, title, source color dot
+ * Oben ein Monatsraster (Nav-Zeile Zurueck/Monat/Weiter, Wochentagskopf,
+ * 42 Zellen ab Montag, Faehrmonatstage gedaempft, heutiger Tag hervorgehoben,
+ * Zaehl-Plakette an Tagen mit Terminen, Tooltip beim Ueberfahren), darunter
+ * der Block "Naechste Termine". Beide Bloecke lassen sich unabhaengig
+ * ein-/ausblenden (Config `showMonth`/`maxEvents`, siehe calendar-month.ts).
+ *
+ * Der Tooltip wird per `createPortal` in `document.body` gerendert, weil die
+ * Karte in widget-wrapper.tsx `overflow-hidden` traegt und ein absolut
+ * positionierter Tooltip sonst abgeschnitten wuerde.
+ *
+ * Das Ladefenster ist IMMER auf lokale Tagesgrenzen gerundet
+ * (`computeFetchWindow`), damit der Backend-Cache-Schluessel
+ * (`${userId}:${from.toISOString()}:${to.toISOString()}`) ueber den
+ * 5-Minuten-Refresh hinweg stabil bleibt — auch wenn die Monatsansicht
+ * ausgeblendet ist, deckt das Fenster weiterhin das 42-Tage-Raster des
+ * (dann immer heutigen) Monats ab, siehe SUMMARY.
+ *
+ * Mehrtaegige/ganztaegige Termine werden im Raster nur am Starttag gezaehlt
+ * (siehe calendar-month.ts).
  *
  * Refreshes every 5 minutes to match the backend cache TTL.
  * NEVER fetches external calendars directly (RESEARCH anti-pattern).
@@ -23,8 +50,22 @@ export function CalendarWidget({ config }: WidgetProps) {
   const [events, setEvents] = useState<CalendarEvent[]>([]);
   const [hasSources, setHasSources] = useState<boolean | null>(null);
   const [isLoading, setIsLoading] = useState(true);
+  const [monthDate, setMonthDate] = useState(() => {
+    const now = new Date();
+    return new Date(now.getFullYear(), now.getMonth(), 1);
+  });
+  const [hover, setHover] = useState<{
+    key: string;
+    rect: { top: number; left: number; bottom: number; right: number };
+  } | null>(null);
   const intervalRef = useRef<ReturnType<typeof setInterval> | undefined>(undefined);
 
+  const { showMonth, maxEvents, lookaheadDays } = useMemo(
+    () => resolveCalendarConfig(config),
+    // eslint-disable-next-line react-hooks/exhaustive-deps
+    [config.showMonth, config.maxEvents, config.lookaheadDays],
+  );
+
   useEffect(() => {
     let cancelled = false;
 
@@ -43,8 +84,10 @@ export function CalendarWidget({ config }: WidgetProps) {
 
         setHasSources(true);
 
-        // Fetch aggregated events from visible sources
-        const eventData = await fetchEvents();
+        // Fetch aggregated events for the current grid/lookahead window —
+        // ALWAYS with both day-boundary ISO strings (T-HTC-03).
+        const { from, to } = computeFetchWindow(monthDate, lookaheadDays);
+        const eventData = await fetchEvents(from.toISOString(), to.toISOString());
         if (cancelled) return;
         setEvents(eventData);
       } catch {
@@ -72,15 +115,35 @@ export function CalendarWidget({ config }: WidgetProps) {
         clearInterval(intervalRef.current);
       }
     };
+    // eslint-disable-next-line react-hooks/exhaustive-deps
+  }, [monthDate.getTime(), lookaheadDays]);
+
+  const showPrev = useCallback(() => {
+    setHover(null);
+    setMonthDate((d) => new Date(d.getFullYear(), d.getMonth() - 1, 1));
   }, []);
+  const showNext = useCallback(() => {
+    setHover(null);
+    setMonthDate((d) => new Date(d.getFullYear(), d.getMonth() + 1, 1));
+  }, []);
+  const showToday = useCallback(() => {
+    setHover(null);
+    const now = new Date();
+    setMonthDate(new Date(now.getFullYear(), now.getMonth(), 1));
+  }, []);
+
+  const eventsByDate = useMemo(() => groupEventsByDate(events), [events]);
+  const days = useMemo(() => buildCalendarDays(monthDate, eventsByDate), [monthDate, eventsByDate]);
+  const upcoming = useMemo(
+    () => selectUpcomingEvents(events, lookaheadDays, maxEvents),
+    [events, lookaheadDays, maxEvents],
+  );
 
   // Loading state
   if (isLoading) {
     return (
       <div className="flex h-full items-center justify-center p-2">
-        <span className="text-sm text-muted-foreground">
-          {t('calendar.loading')}
-        </span>
+        <span className="text-sm text-muted-foreground">{t('calendar.loading')}</span>
       </div>
     );
   }
@@ -89,74 +152,167 @@ export function CalendarWidget({ config }: WidgetProps) {
   if (hasSources === false) {
     return (
       <div className="flex h-full items-center justify-center p-2">
-        <span className="text-sm text-muted-foreground">
-          {t('calendar.emptyNoSources')}
-        </span>
+        <span className="text-sm text-muted-foreground">{t('calendar.emptyNoSources')}</span>
       </div>
     );
   }
 
-  // Sources exist but no events
-  if (events.length === 0) {
+  // Both blocks hidden by configuration
+  if (!showMonth && maxEvents === 0) {
     return (
       <div className="flex h-full items-center justify-center p-2">
-        <span className="text-sm text-muted-foreground">
-          {t('calendar.emptyNoEvents')}
-        </span>
+        <span className="text-sm text-muted-foreground">{t('calendar.nothingSelected')}</span>
       </div>
     );
   }
 
-  // Events list
+  const hoverEvents = hover ? (eventsByDate.get(hover.key) ?? []) : [];
+
   return (
-    <div className="flex h-full flex-col overflow-y-auto p-1.5">
-      <ul className="space-y-2">
-        {events.map((event) => (
-          <li
-            key={event.id}
-            className="flex items-start gap-2 rounded px-2 py-1.5 text-sm hover:bg-muted/50"
+    <div className="flex h-full flex-col gap-1 overflow-hidden p-1.5">
+      {showMonth && (
+        <div data-testid="calendar-month" className="flex shrink-0 flex-col gap-1">
+          {/* Nav-Zeile */}
+          <div className="grid grid-cols-[1fr_1.4fr_1fr] gap-1">
+            <button
+              type="button"
+              className="widgetNoDrag rounded border border-border bg-muted/50 px-1 py-[clamp(2px,0.8cqh,6px)] text-[clamp(10px,2.6cqw,13px)] leading-none text-foreground hover:bg-muted"
+              onClick={showPrev}
+            >
+              {t('calendar.monthPrev')}
+            </button>
+            <button
+              type="button"
+              className="widgetNoDrag truncate rounded border border-border bg-muted/50 px-1 py-[clamp(2px,0.8cqh,6px)] text-[clamp(10px,2.6cqw,13px)] font-semibold leading-none text-foreground hover:bg-muted"
+              title={t('calendar.monthToday')}
+              onClick={showToday}
+            >
+              {formatMonthLabel(monthDate)}
+            </button>
+            <button
+              type="button"
+              className="widgetNoDrag rounded border border-border bg-muted/50 px-1 py-[clamp(2px,0.8cqh,6px)] text-[clamp(10px,2.6cqw,13px)] leading-none text-foreground hover:bg-muted"
+              onClick={showNext}
+            >
+              {t('calendar.monthNext')}
+            </button>
+          </div>
+
+          {/* Wochentagskopf */}
+          <div className="grid grid-cols-7 gap-px text-center text-[clamp(9px,2.2cqw,12px)] font-medium text-muted-foreground">
+            {WEEKDAY_LABELS.map((label) => (
+              <div key={label}>{label}</div>
+            ))}
+          </div>
+
+          {/* Raster */}
+          <div className="grid grid-cols-7 gap-px">
+            {days.map((day) => {
+              const hasEvents = day.events.length > 0;
+              const cellClass = [
+                'widgetNoDrag relative flex min-h-[clamp(16px,5.5cqh,40px)] items-start rounded bg-muted/50 px-1 py-0.5 text-[clamp(9px,2.4cqw,13px)] leading-none',
+                day.inCurrentMonth ? 'text-foreground' : 'text-muted-foreground/60',
+                day.isToday ? 'ring-1 ring-primary font-semibold text-primary' : '',
+                hasEvents ? 'cursor-default hover:bg-muted' : '',
+              ]
+                .filter(Boolean)
+                .join(' ');
+
+              return (
+                <div
+                  key={day.key}
+                  data-testid="calendar-day"
+                  data-date={day.key}
+                  data-today={day.isToday || undefined}
+                  data-outside={!day.inCurrentMonth || undefined}
+                  className={cellClass}
+                  onMouseEnter={(e) =>
+                    hasEvents &&
+                    setHover({ key: day.key, rect: e.currentTarget.getBoundingClientRect() })
+                  }
+                  onMouseLeave={() => setHover(null)}
+                >
+                  <span>{day.date.getDate()}</span>
+                  {hasEvents && (
+                    <span
+                      data-testid="calendar-day-count"
+                      className="absolute bottom-px right-px flex h-[clamp(10px,3cqw,16px)] min-w-[clamp(10px,3cqw,16px)] items-center justify-center rounded-full bg-primary px-0.5 text-[clamp(7px,1.8cqw,10px)] font-semibold leading-none text-primary-foreground"
+                    >
+                      {day.events.length}
+                    </span>
+                  )}
+                </div>
+              );
+            })}
+          </div>
+        </div>
+      )}
+
+      {maxEvents > 0 && (
+        <section className="flex min-h-0 flex-1 flex-col gap-1">
+          <h3 className="shrink-0 text-[clamp(10px,2.6cqw,13px)] font-semibold text-foreground">
+            {t('calendar.upcomingTitle')}
+          </h3>
+          {upcoming.length === 0 ? (
+            <p className="text-[clamp(9px,2.2cqw,12px)] text-muted-foreground">
+              {t('calendar.emptyNoEvents')}
+            </p>
+          ) : (
+            <ul data-testid="calendar-upcoming" className="min-h-0 flex-1 space-y-1 overflow-y-auto">
+              {upcoming.map((event) => (
+                <li key={event.id} className="flex items-start gap-2 rounded bg-muted/50 px-2 py-1">
+                  <span
+                    data-testid="event-color-dot"
+                    className="mt-1 h-2 w-2 shrink-0 rounded-full"
+                    style={{ backgroundColor: event.color || 'var(--muted-foreground)' }}
+                    aria-hidden="true"
+                  />
+                  <div className="min-w-0 flex-1">
+                    <p className="truncate text-[clamp(9px,2.2cqw,12px)] text-muted-foreground">
+                      {formatEventDate(event)}
+                    </p>
+                    <p className="truncate text-[clamp(10px,2.5cqw,14px)] font-semibold text-foreground">
+                      {event.title}
+                    </p>
+                    {event.location && (
+                      <p className="truncate text-[clamp(9px,2.1cqw,12px)] text-muted-foreground">
+                        {event.location}
+                      </p>
+                    )}
+                  </div>
+                </li>
+              ))}
+            </ul>
+          )}
+        </section>
+      )}
+
+      {hover !== null &&
+        typeof document !== 'undefined' &&
+        createPortal(
+          <div
+            data-testid="calendar-day-tooltip"
+            role="tooltip"
+            className="pointer-events-none fixed z-50 w-60 rounded border border-border bg-card p-2 text-xs text-foreground shadow-lg"
+            style={{
+              top: hover.rect.bottom + 4,
+              left: Math.max(4, Math.min(hover.rect.left, window.innerWidth - 244)),
+            }}
           >
-            {/* Source color dot (8px, UI-SPEC) */}
-            <span
-              data-testid="event-color-dot"
-              className="mt-1.5 h-2 w-2 shrink-0 rounded-full"
-              style={{ backgroundColor: event.color || 'var(--muted-foreground)' }}
-              aria-hidden="true"
-            />
-            <div className="flex-1 min-w-0">
-              <p className="truncate font-medium text-foreground">
-                {event.title}
-              </p>
-              <p className="text-xs text-muted-foreground">
-                {formatEventTime(event)}
-              </p>
-            </div>
-          </li>
-        ))}
-      </ul>
+            {hoverEvents.slice(0, 5).map((event) => (
+              <div key={event.id} className="flex gap-2">
+                <span className="shrink-0 tabular-nums text-muted-foreground">
+                  {event.allDay ? t('calendar.allDay') : formatEventTime(event.start)}
+                </span>
+                <span className="truncate">{event.title}</span>
+              </div>
+            ))}
+            {hoverEvents.length > 5 && (
+              <div className="mt-1 text-muted-foreground">{t('calendar.tooltipMore')}</div>
+            )}
+          </div>,
+          document.body,
+        )}
     </div>
   );
 }
-
-/**
- * Format event time using locale-aware Intl.DateTimeFormat.
- * All-day events show only the date; timed events show time range.
- */
-function formatEventTime(event: CalendarEvent): string {
-  const start = new Date(event.start);
-  const end = new Date(event.end);
-
-  if (event.allDay) {
-    return new Intl.DateTimeFormat('de-DE', {
-      day: '2-digit',
-      month: 'short',
-    }).format(start);
-  }
-
-  const timeFormatter = new Intl.DateTimeFormat('de-DE', {
-    hour: '2-digit',
-    minute: '2-digit',
-  });
-
-  return `${timeFormatter.format(start)} – ${timeFormatter.format(end)}`;
-}